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The cover photographs show health-care facilities in (from top to bottom) Myanmar, South Africa, Peru, Nepal, Hong Kong SAR and Nepal.

Cover designed by Design ONE, Canberra, Australia Production and design by Biotext, Canberra Contents Foreword

vi Natural Ventilation for Infection Control in Health-Care Settings Figure C.1 (A) Schlieren image (visualization using light refraction caused by differences in air density) of a human cough, and (B) flash photo of a human sneeze

Figure C.2 The Wells evaporation-falling curve of droplets

Figure C.3 Patterns of air exchange during daily activities

Figure F.1 Hospital Nacional Dos de Mayo

Figure F.2 Floor plan and photos of different wards in Hospital Nacional Dos de Mayo

Figure G.1 Open wards and windows in the tuberculosis ward in Grantham Hospital

Figure G.2 A ceiling fan for summer cooling and a radiator for winter heating............. 96 Figure G.3 Ambient air temperature, wind speed and wind direction measured by the Hong Kong Observatory at Wong Chuk Hang weather station, close to the Grantham Hospital

Figure H.1 Two views of the single-storey tuberculosis inpatient ward; the perimeters are free from obstruction, allowing natural ventilation throughout the year

Figure H.2 Floor plan of tuberculosis unit inpatient ward

Figure H.3 Inside the tuberculosis inpatient ward

Figure I.1 The IOM Holding Centre in Damak

Figure I.2 Individual isolation unit (left), and the gap between the vertical wall and the roof for natural ventilation (right)

vii

Contents

Foreword In June 2007, the World Health Organization (WHO) released a guideline document on infection prevention and control entitled Infection prevention and control of epidemic- and pandemic-prone acute respiratory diseases in health care — WHO interim guidelines (WHO, 2007). In this new guideline, natural ventilation is considered for the first time among the effective measures to control infections in health care. Such a recommendation from WHO demonstrates a growing recognition of the role of ventilation and natural ventilation for infection control.

The 2007 guideline demonstrated that further study was required in areas such as minimum requirements for natural ventilation and design, construction, operation and maintenance for effective natural ventilation systems for infection control.

Over the past two years, a multidisciplinary team of engineers, architects, infection-control experts and microbiologists has been working to produce this WHO guideline, providing a design and operation guide for hospital planners, engineers, architects and infectioncontrol personnel. The recommendations in this WHO guideline followed a systematic review of the literature on the association of ventilation and disease transmission, as well as effective natural ventilation solutions for infection control.

This WHO guideline should be used in conjunction with other relevant infection-control guidelines.

There are very few studies on natural ventilation for infection control in hospitals. The authors of this guideline have attempted to document what is known today. Any comments from the users and readers of this guideline will be useful for future revisions and further information may be obtained at http://www.who.int/csr/natvent (and follow the ‘natvent’ links), or at http://www.who.int/csr/bioriskreduction/natvent/en/.

We would like to acknowledge the collaboration and generous financial support provided by the French Ministry of Health, Youth and Sport that has made the development and production of this guideline possible.

We also acknowledge the United States Agency for International Development for financial support for the development and publication of this document.

We also thank the Research Grants Council Fund for the Control of Infectious Diseases and the Hospital Authority of Hong Kong SAR for providing funding for research and field measurements for the development of this guideline.

We also thank the Asia Pacific Society of Infection Control for supporting the first multidisciplinary consensus meeting on the use of natural ventilation for infection control, 15–17 May 2007.

Finally, we thank the staff and management of the facilities used as examples in this guideline for their support and contribution.

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